Valves are ubiquitous for regulating, controlling, and isolating fluids within conduits. Whether for transmission/distribution of gas, oil, water, or within an industrial process, valves play a critical role in maintaining efficient, safe, and reliable system operation. Valve failure can lead to system inefficiencies, the inability to assess/control the system's operational state, or catastrophic system failure.
In water distribution systems, valves are primarily used for two purposes: flow/pressure control and isolating subsystems. Subsystem isolation is required to perform repairs or to isolate contaminants. Based on water utility surveys, typically over 85% of the valves within the distribution network are used for isolation. Buried gate valves with valve boxes are typically used for isolation of small-diameter water mains, over 90%, and butterfly valves, approximately 1%, are direct buried or installed in chambers and are typically used for large diameter mains. Typical valve density is between 10 to 20 valves per linear mile of distribution water mains and at least 2 to 3 valves per mile of transmission mains.
Isolation valves are prone to deterioration and failures, such as stripped, broken, or bent stems; leaking O-rings or packing; sedimentation or tuberculation preventing full closure, corrosion of the valve body and connecting bolts; and wear on the valve disk and seat. Based on water utility surveys, utilities reported that nonfunctioning valves were found under emergency situations on average 9% of the time and annually between 1 and 12 valve malfunctions were found per 100 linear miles of water mains. As another datum on the importance of valve reliability, a study conducted by the Boston Water and Sewer Commission found 120 out of 2800 isolation valves could not be operated, i.e., 4.3%. In addition to valve operational failure, there is operator failure to correctly set the desired operational setting for the valve, e.g., open or closed. This can be caused by having a mixture of left and right handed valves in the system, as well as due to variations in the number of turns required to set the desired valve state. Utilities reported, on average, 2 times/year valves were set in the wrong position because of left-hand/right-hand confusion.
Isolation valves left in the incorrect state or closed cause operational hazards: inefficiencies and “dead end” segments. Back pressure and incorrect flow patterns caused by closed valves cause reduced flow rates requiring increased pumping to deliver the required pressure to customers. This requires additional “wasted” energy or, in the worst case, additional capacity is provided by adding pipe lines to the distribution network. In addition, closed isolation valves cause “dead end” line segments in which water stagnates and sediment builds up. When the valve is opened, stagnate (and possibly septic) water is released, causing a potential health risk to customers downstream.
In gas and oil transmission/distribution systems and industrial process systems, valves are used widely on installations for controlling the flow of fluids. The type of valve is dependent on the application, with common valve types being bleed, block, check, choke, control, relief, and emergency shutdown. Valve failure can be caused by a number of issues, with failure modes grouped into two general categories: fugitive emissions and operational failure. Fugitive emissions are caused by valve leakage at the stem to the environment outside the pipe. This mode of failure is not addressed by the present invention. The invention is designed to address operational (including mechanical) failures, such as: failure to fully open, failure to fully close, failure to operate, and failure to seal. In addition, valve operational failure is often caused by operator error, e.g., leaving a valve partially open. To illustrate, in one example, 40% of the block valve failures were due to the valve being left at least partially open, with an additional 25% due to defective operating procedures. Minimizing operational failures requires a regimen of inspection and maintenance with effective operating procedures to minimize operator error.
Various valve leak detection techniques and systems have been developed using passive detection techniques, i.e., transducers are used to detect the pressure wave caused by a valve leaking. For example, the Powell and Dimick invention (U.S. Pat. No. 5,650,943) is based on passive acoustic detection at three locations upstream, downstream, and at the valve. Detection is based on an acoustic signal generated by the valve leaking and the three acoustic signatures are used for valve leak detection. The Farstad and Cremean invention (U.S. Pat. No. 5,361,636) is based on using an accelerometer attached to a pipe wall to measure the acoustic pressure wave generated by a fluid within a pipe resulting from a valve leak. The Leon and Heagerty inventions (U.S. Pat. Nos. 6,128,946 and 6,134,949) are based on passive detection of pressure wave transient at both the upstream and downstream from an emergency shutdown valve. The detected transient waves are evaluated to detect a leaky valve. The Balaschak invention (U.S. Pat. No. 5,616,829) is based on using a vibration sensor to detect leakage. When vibration is detected, a driving unit for the valve stem is used to fully seat the valve. The Kumpfmueller (U.S. Pat. No. 6,530,277) and Fiebelkorn (U.S. Pat. No. 6,637,267) and Ens and Püttmer (U.S. Pat. No. 6,976,503) inventions are based on using body sound spectra on the valve in conjunction with a position controller. The spectra are recorded in both open and closed position and are stored to be used in evaluating a non-sealed condition.
The following address inventions limited to valve state detection using passive detection techniques. The Ens and Püttmer invention (U.S. Pat. No. 7,621,179) is based on passive detection of the solid-borne sound spectrum for a check valve in both the closed and open states. The detection timing is conducted to reduce ambient noise such that the sound spectrum in the check valve's two states is used to determine if the valve is seating correctly. The Taylor invention (U.S. Pat. No. 6,685,638) is based on detecting the audible “click” produced by the valve in order to determine the position of the valve where the valve's position is controlled by a stepper motor. The Cobb invention (U.S. Pat. No. 4,896,101) uses trend analysis in changes in power, temperature, motor noise, and downstream fluid flow noise to monitor electro-mechanical or pneumatically driven valves. The Abdel-Malek invention (U.S. Pat. No. 5,616,824) is based on evaluating the electromechanical response for an electromechanical control valve to assess the valve's condition. The Stewart and Foresman invention (U.S. Pat. No. 7,784,490) is based on the valve stem having an activator, e.g., a magnet, which can be sensed to determine the valve's position. The Breen invention (U.S. Pat. No. 7,313,497) is based on measuring the pressure differential across a valve. The measured differential is compared to the required differential to evaluate the valve's condition.
The McShane and Ulerich invention (U.S. Pat. No. 5,115,672) uses an active ultrasonic transducer pair (transmitter and receiver) to interrogate the fluid flow in the cross section of the pipe downstream from the valve. The transducers are attached to the outside of the pipe wall. The signature of the received transmission through a turbulent fluid is used to estimate the valve's condition. Even though this approach uses an active transmission, it is measuring the cross-sectional characteristics of the fluid flow and not directly evaluating the transmission/reflection characteristics of the valve.
The following address inventions to assist in maintaining valves in a water distribution system. The Murphy invention (U.S. Pat. No. 6,125,868) uses a portable computerized system in conjunction with a robotic valve turning machine used to exercise and record the operation results. The Buckner and Buckner invention (U.S. Pat. No. 8,033,299) is based on a combined vacuum, water jetter, and valve actuator used for a valve exercise program.
The following address inventions to determine valve characteristics/state through system monitoring. The Schoonover invention (U.S. Pat. No. 7,089,086) is based on observing valve information while a valve operates in response to control signals which systematically exercise the valve. During normal operation, valve characteristics are then determined based on collected valve information. The Pyötsia invention (US 2011/0295407) is based on monitoring the system process to identify the operating points for the valves.
Thus, a primary application for the related art is valve leak detection due to a faulty valve seating. A number of the inventions exploit passive detection of the pressure wave caused by turbulence when the valve does not seat. One invention uses active detection to interrogate the pipes cross-section downstream of the pipe. Both the active and the passive detection inventions are based on indirect evaluation of the valve-state exploiting the turbulence caused by the valve not seating to classify the valve-state. These approaches also require placement of sensors either on or near the valve-under-test. In addition, the related art has taught that augmenting the valve with mechanical and/or electrical attributes can provide valve-state information. A limitation of these approaches is that failure of the mechanical and/or electrical attributes will result in a false valve-state-estimation.